is osx

Hunt Hypothesis

This detection identifies macOS-specific file artifacts and execution patterns that may indicate an adversary establishing a foothold or exfiltrating data within Apple environments. Proactively hunting for these signals in Azure Sentinel is critical to validate endpoint visibility across hybrid infrastructures and ensure low-severity macOS activities are not overlooked during broader incident response efforts.

YARA Rule

rule is__osx
{
 meta:
    date = "2018-02-12"
    author = "@unixfreaxjp"
 condition:
    uint32(0) == 0xfeedface     or uint32(0) == 0xcafebabe
    or uint32(0) == 0xbebafeca  or uint32(0) == 0xcefaedfe
    or uint32(0) == 0xfeedfacf  or uint32(0) == 0xcffaedfe
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints
• Source Rule

False Positive Guidance

Here are specific false positive scenarios for the is_osx detection rule in an enterprise environment, along with recommended filters and exclusions:

• Automated macOS System Updates via MDM

  • Scenario: The rule triggers on legitimate background processes initiated by Mobile Device Management (MDM) solutions like Jamf Pro, Microsoft Intune, or JAMF Now. These tools frequently push OS updates, security patches, or configuration profiles that spawn temporary softwareupdate or migrator daemons across the fleet.
  • Filter/Exclusion: Exclude processes where the parent process is a known MDM agent (e.g., JamfAgent, IntuneManagementExtension) and the command line arguments contain keywords like --install-update or --apply-policy.

• Scheduled Antivirus Scans by Endpoint Protection Suites

  • Scenario: Enterprise-grade endpoint protection tools such as CrowdStrike Falcon, SentinelOne, or Carbon Black perform scheduled deep scans. These scans often spawn multiple child processes (e.g., falcon-sensor, s1agent) that access the OS kernel and file system extensively, mimicking the behavior of a new OS installation or configuration change detected by the YARA rule.
  • Filter/Exclusion: Create an exclusion list for known EDR executable paths (e.g., /Library/Application Support/CrowdStrike/Falcon/falcon-sensor) and exclude events occurring during defined maintenance windows (e.g., 02:00–04:00 local time).

• Software Deployment via Package Management Tools

  • Scenario: IT administrators use package management tools like Munki, Big Sur, or Homebrew to deploy enterprise applications. When these tools install software, they execute scripts that modify system libraries and registry-like plist files, triggering